The investigation on the photocatalytic activity of Ho doped nano TiO₂

A series of Ho-doped and un-doped TiO₂ nanoparticles were prepared by sol-gel method with tetra-n-butyl titanate as raw material. The samples were characterized with TG-DTA, X-ray diffraction (XRD), and UV-Vis absorption spectra, and their photocatalytic activity were studied by photocatalytic depigmentation of methyl orange in water. The result showed that Ho doping not only restrained the growth of TiO₂ grain size, but also led to the expansion and matrices distortion of crystal lattices. A tiny blue-shift of the absorption profile and two absorption peaks around at 450 and 540 nm were found by the UV-Vis absorption spectra in Ho-doped samples. Appropriate content Ho doping improved the photocatalytic activity of TiO₂. The photocatalytic activity of 0.3 mol% Ho-doped TiO₂ nanoparticles is optimal of all the prepared samples under UV irradiation. Ho-doped TiO₂ took on excellent photocatalytic activity under visible light (wavelength (λ)>420 nm) irradiation and depigmentation ratio of methyl orange reached to 21.6% in 210 min.